This paper discuses identifying of lithology of The Lidam carbonate reservoir of Gialo oil Field in Sirte basin by means of well log data. The Lidam Formation is unconformably overlies the Nubian formation and underlies Lower Sirte shale representing an age Cenomanian time (U. Cretaceous).
In this study, well log data analysis has been performed. The analysis includes values of gamma ray, resistivity, neutron, density and sonic log data. This analysis is being obtained from different types of logging tools. These values of well log data are plotted on several diagrams of Schlumerger. This shows different location of sedimentary facies and mineral composition of the studied formation according to their content of elements which reflect particular rock type. Available well log data on Lidam reservoir rock suggest that the formation in this area is an average thickness about 90 feet included limestone, dolomite and anhydrite. The studied interval of Lidam reservoir is dominated by sediments interpreted as Lagoonal to tidal flat setting (supratidal, intertidal and subtidal environments).